sin^2a*tana+cos^2a/tana+2sina*cosa
=(1-cos^2a)*tana+(1-sin^2a)/tana+2sina*cosa
=tana-sina*cosa+1/tana-sina*cosa+2sina*cosa
=tana+1/tana
sin^2a*tana+cos^2a/tana+2sina*cosa
=(1-cos^2a)*tana+(1-sin^2a)/tana+2sina*cosa
=tana-sina*cosa+1/tana-sina*cosa+2sina*cosa
=tana+1/tana